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[forcan]

Started my first build - the Aberdeen Pilot Boat "Sea Shepherd", from the plans in Model Boats. Now building it isn't the problem, but figuring out the electronics required to make it go is!!!  I have the rudder and propshafts installed (It's a twin-prop hull), the hull is approx 750mm long, and I've a pair of 45mm props to go on it. Been fibreglassing the hull over the last week

So the electrics... The rudder is easy - a servo install I can do - but I'd appreciate some advice on the rest of the gear, appropriate battery choice, speed controller, motors etc

Cheers!

[thething84]

not sure on motor. My tug i am putting a 540 size motor running on 6v powering 45mm steerable kort.
 
Batteries. I would say put as big batteries as you can fit weight wise. The bigger amperage the longer run time you will have. Also means less ballast later on.
 
normally they say what they are putting in it in the magazine.
 
James

[malcolmfrary]

If its the same boat there's a link here - http://www.maritimejournal.com/news101/vessel-build-and-maintenance/vessel-launch/macduffs_new_pilot_launch_for_aberdeen_harbour_board
Information from reading the link gives a model scale of 1:20, the power info suggests a pair of 385 motors running on about their rated voltage to give the appropriate power to give a speed of about 4mph (which scales about right).  One motor per shaft and an ESC per motor (rated in the 10-15A range) should give the same maneuverability as the real thing, as opposed to one motor and associated gearing.
There will normally be an indication of motor size on the plan, and if the plan came with the article, that will usually give clues.
As was suggested for batteries, as much as it can stand.  Bear in mind that the total weight of the boat will be about 12 lb.  I would be looking for some nice big NiMH packs, probably 2 sticks of 4 to hook up in series to give 9.6 volts.  2 sticks is vastly easier to site where wanted than one big lump.
Edit - just had another look at the list that goggle threw up - heres another link -
http://www.partworkmodels.co.uk/phpBB3/viewtopic.php?f=37&t=1243
This builder seems to have gone to town on motors, more than I would have done, but maybe that was what was suggested in the plans.

[inertia]

I have reservations about 385 motors being able to spin 45mm props. I'd suggest 555's (Component Shop stock them) on 12v.
DM

[john44]

I have reservations about 385 motors being able to spin 45mm props. I'd suggest 555's (Component Shop stock them) on 12v.
DM

I second those reservations Dave.
385,s spinning 45mm props? not for long before meltdown.
Not on direct drive anyway.

john

[malcolmfrary]

That's why I had a look at the other link -[size=0px]http://www.partworkmodels.co.uk/phpBB3/viewtopic.php?f=37&t=1243[/size][/color]  .  It did seem to me that 45mm props might be a bit big for a 2 and a bit foot boat.
Apart from the traditional rule of thumb that the prop diameter should not exceed the motor can diameter, I was given another "rule" years ago - "the motor should have more poles than the prop has blades".  With 5 blade props (which this prototype seem to have) this points at using gearboxes or belt reduction.  Smaller motors might well be OK in that case.

[inertia]

The 500E's no load RPM on 12v is 12000, which is hellish quick for a model/prop combination like this. You could reduce the voltage to 6v but that's cutting down the power to those big props. My original Sentinel used nice soft 545 motors geared down 2:1 to turn 5-blade props on 7.2v and I'm certain the props aren't as big as 45mm (about 37mm from memory). If 't were mine I'd use 35mm x 4 blade props on the aforementioned 555 motors direct drive. as a starting point.
As for the rest of the electrickery, have a shufti here http://www.action-electronics.co.uk/pdfs/Basic%20P94%20set-up.pdf
Suit yourself, as someone once said.
DM

[Davenotdone]

My setup?  Dickie tug conversion, 6v 385 type motor on a 40mm 4 blade prop direct drive. Result, one burnt out motor. Prop too big!   Now, MFA 385, still 6v but now running a 30mm brass scale type 3 blade prop. Result?  smooth as  silk, nice 'scale' type speed and motor just barley warm and run's for a least 1 hour or i get bored. Don't over prop your motor as i found out!!!    Regards, Dave.

[forcan]

Just the very information I was after - Thanks folks!